HCl Molecules Research Articles

Palladium-Catalyzed C(sp3)-H Activation in A Monoterpene-Based Compound Under Mild Conditions: A Combined Experimental and Theoretical Mechanistic Study.

A rare example of the palladium-catalyzed sp3 C-H bond activation in a monoterpene-based compound has been observed in the reaction of PdCl2 with a (+)-3-carene-based ligand HL (HL=N-((1aS,3S,7bR)-1,1,3-trimethyl-7-phenyl-5-(pyridin-2-yl)-1a,2,3,7b-tetrahydro-1H-cyclopropa[f]quinolin-3-yl)acetamide), which yielded the [PdLCl] complex. In contrast to the vast majority of C(sp3)-H activation reactions which require prolonged heating and mixing due to the inert character of the corresponding bond, the reaction reported herein proceeds rapidly under mild conditions. A theoretical insight into the ligand deprotonation has been performed by DFT calculations. The mechanism of the C-H activation involves (i) simultaneous coordination of the CH3 group of HL to the Pd2+ ion and decoordination of the Cl- anion with consequent formation of a Cl⋅⋅⋅H-N hydrogen bond with the amide group, (ii) approximation of the out-of-sphere Cl- anion to one of the hydrogen atoms of the CH3 group mediated by the crane motion of the amide group and (iii) the ejection of the HCl molecule, which increases the entropy of the system and serves as a driving force for the reaction.

Development of a ReaxFF Reactive Force Field for Pt/Cl Systems with Application to Platinum Metal Etching with Chlorine and Hydrogen Chloride Gases.

In this study, we present the development of a ReaxFF Pt/Cl/H reactive force field designed to elucidate the etching process by Cl for Pt surfaces. The ReaxFF force field parameters were optimized based on a quantum mechanical training set, which included adsorption energies of Cl and dissociation of HCl on Pt(100) and Pt(111) surfaces, energy/volume relations of PtCl2 crystals, and Cl diffusion on Pt(100) and Pt(111) surfaces. The predictive capability of the force field was further established through molecular dynamics simulations, which investigated the interactions of Cl2 and HCl molecules with the (100) and (111) surfaces of c-Pt crystalline solid slabs. A comparative analysis revealed that the Pt (100) surface exhibited higher susceptibility to chlorination and etching, leading to a more dominant removal of surface Pt atoms, whereas the Pt (111) surface showed greater resistance to these processes. This resistance impeded the access of Cl atoms to the Pt surface, resulting in a slower formation of PtxCly molecules. The etching ratios between HCl and Cl2 were compared with experimental results, yielding satisfactory agreement. This indicates that the developed ReaxFF protocol serves as a valuable tool for studying atomistic-scale details of the etching process in platinum metal systems.

A cobalt templated outer sphere hydrogen bond donor catalyst derived from 2-guanidinobenzimidazole: Synthesis, applications in carbon–carbon bond forming reactions, structure

A lipophilic tricationic cobalt tris(chelate) complex of 2-guanidinobenzimidazole (GBI), [Co(GBI)3]3+ 3BArf– (23+ 3BArf–; BArf = B(3,5-C6H3(CF3)2)4), is prepared from the corresponding hydrophilic trichloride salt and Na+ BArf– or Ag+ BArf– under aqueous/organic biphasic conditions. This racemic chiral complex, which is obtained as a mer isomer and a tetradecahydrate as assayed by NMR and TGA, is an excellent catalyst for additions of dimethyl malonate and indole to trans-ß-nitrostyrenes (10 mol%), and cycloadditions of CO2 to epoxides (1 mol%; solvent-free). Average yields (84 %, 91 %, 81 %) and rates are slightly greater than those obtained with a monocationic ruthenium GBI complex [(η5-C5H5)Ru(CO)(GBI)]+ BArf– prepared earlier. Attempted crystallization of 23+ 3Cl– gives a tetramethanol solvate of a salt derived from loss of two molecules of HCl. This can be represented as [Co(GBI)(GBI–H)2]+ Cl−, and bond lengths and hydrogen bonding motifs are carefully analyzed, especially in the context of dominant chelate resonance forms.

Identifying isotopes in HCl gas using high-resolution terahertz absorbance spectroscopy

This study presents a novel method for identifying the isotopes H35Cl and H37Cl using a unique high-resolution terahertz (THz) spectroscopy system. To prevent the absorbance of water vapor, chlorodimethylsilane (DMCS) was used as the source of HCl gas. Our analysis revealed periodic peaks at ∼1.9, 2.5, 3.1, 3.7, 4.4, 5.0, and 5.6 THz. Notably, we observed double peaks in the HCl isotopes H35Cl and H37Cl. The results were analyzed using least-square fitting, which showed that themeasurements agreed extremely well. The obtained peaks correlated with the rotational constants of HCl molecules, including 6B, 8B, 10B, 12B, 14B, 16B, and 18B.

Cooperativity between Intermolecular Hydrogen and Carbon Bonds in ZY···CH3CN/CH3NC···HX Trimers (ZY = H2O, H2S, HF, HCl, HBr, NH3, and H2CO; HX = HF, HCl, and HBr).

Hydrogen-bonding and carbon-bonding interactions are widespread in nature. We studied the cooperativity between these interactions in 42 trimeric complexes ZY···CH3CN/CH3NC···HX, where ZY molecules are H2O, H2S, HF, HCl, HBr, NH3, and H2CO, and HX molecules are HF, HCl, and HBr. Acetonitrile (CH3CN) and isoacetonitrile (CH3NC) act as hydrogen bond acceptors as well as carbon bond donors in these trimers. Various theoretical methods, such as electronic structure calculations, quantum theory of atoms in molecule (QTAIM), natural bond orbital (NBO), and reduced density gradient analysis, are employed to study these trimers, and the results are compared with the corresponding ZY···CH3CN/CH3NC and CH3CN/CH3NC···HX dimers. Electronic structure calculations are performed at the second-order Mo̷ller-Plesset perturbation theory using the 6-311++G(2d,2p) basis set. We show that both the interactions act synergistically in these trimers leading to an increase in their bond strength as compared to the strength in the individual dimers. The cooperative energies for these trimers are in the range of 0.69 to 3.22 kJ/mol. It is seen that the carbon bonds benefit more from the cooperativity than the hydrogen bonds. The trends of cooperativity and correlations of interaction energies and cooperative energies with relevant QTAIM and NBO parameters are reported.

A noval salt effect coupled vacuum distillation process for high efficient ultra-azeotropic reuse of spent HCl

The escalating challenge of recycling and treating spent hydrochloric acid (HCl) in various industries, driven by stringent environmental regulations, necessitates urgent solutions for the reuse of spent HCl in industrial processes. However, the concentration and reuse of spent HCl have been impeded by azeotropism. In this study, an innovative salt effect coupled vacuum distillation process was introduced to enable the rapid and convenient recovery of HCl. Salts and vacuum environment both can be found to break the azeotropism effectively, augment the disparity in the dissociation abilities of HCl and H2O in clusters, and enhance the evaporation rate. Specifically, MgCl2 and CaCl2 salt systems were selected, achieving recovered HCl concentrations of 9.66 and 9.85 mol/L, with corresponding recovery rates of 86.45 % and 80.65 %, respectively. For the reuse of spent HCl from chlorinated distillation for extracting germanium (Ge), the presence of As(V) poses a risk to Ge recovery and potential contamination of the Ge product. Excellent resistance to As(Ⅴ) mobilization (<2%) was obtained in the CaCl2 system. To comprehensively understand the salt’s role in breaking azeotropism, molecular simulations were employed. The Mg2+/Ca2+ ions were observed to bind with H2O molecules in the solution, weakening the force between H2O and HCl, decreasing the dissociation energy of HCl molecules by 35 times (from 102.82 to 2.94 kJ/mol), and increasing the dissociation energy of H2O molecules from 52.5 to 61.5 kJ/mol. The proposed process integrates high HCl recovery with an ultra-azeotropic concentrating effect, offering a novel approach for reusing spent HCl in industrial applications.

Why do dipole moments of HCl-water clusters fail to determine acid dissociation?

This paper quantitatively examines why dipole moments of HCl(H2O)n=1-8 cannot serve as the dissociation criterion for acid molecules using the Hirshfeld-I approach. Also, we propose the possible experimental parameter 〈P(HCl)〉, whose statistical average enables the assessment of acid dissociation in mixed clusters. Furthermore, our calculations reveal that a minimum of four water molecules are necessary to dissociate an HCl molecule.

N^N^C-Cyclometalated rhodium(III) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity.

The impact of isomerism of pyrimidine-based ligands and their rhodium(III) complexes with regard to their structures and properties was investigated. Two isomeric ligands, 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,5-diphenylpyrimidine (HL2,5) and 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,6-diphenylpyrimidine (HL2,6), were synthesized. The ligands differ by the degree of steric bulk: the molecular structure of HL2,5 is more distorted due to presence of pyrazolyl and phenyl groups in the neighbouring positions 4 and 5 of the pyrimidine ring. The complexation of HL2,5 and HL2,6 with RhCl3 leads to the sp2 C-H bond activation, resulting in the isolation of two complexes, [RhL2,5(Solv)Cl2]·nEtOH and [RhL2,6(Solv)Cl2]·nEtOH (Solv = H2O, EtOH), with the deprotonated forms of the pyrazolylpyrimidine molecules which coordinate the Rh3+ ion as N^N^C-tridentate ligands. According to DFT modelling, the mechanism of the deprotonation involves (i) the C-H bond breaking in the 2-phenyl group followed by the coordination of the C atom to the Rh atom, (ii) the protonation of coordinated chlorido ligand, (iii) the ejection of the HCl molecule and (iv) the coordination of the H2O molecule. The ligand isomerism has an impact on emission properties and cytotoxicity of the complexes. Although the excited states of the complexes effectively deactivate through S0/T1 and S0/S1 crossings associated with the cleavage of the weak H2O ligands upon excitation, the [RhL2,5(Solv)Cl2]·nEtOH complex appeared to be emissive in the solid state, while [RhL2,6(Solv)Cl2]·nEtOH is non-emissive at all. The complexes show significant cytotoxic activity against cancerous HepG2 and Hep2 cell lines, with the [RhL2,6(Solv)Cl2]·nEtOH complex being more active than its isomer [RhL2,5(Solv)Cl2]·nEtOH. On the other hand, noticeable cytotoxicity of the latter against HepG2 is supplemented by its non-toxicity against non-cancerous MRC-5 cells.

Assessment of Approximations to the Embedding Potential in Frozen-Density Embedding Theory for the Calculation of Electric Field Gradients.

The approximations to the embedding potential in frozen-density embedding theory (FDET) have been assessed for the first time for the calculation of the electric field gradient (EFG) at a nucleus. FDET-based methods using a hierarchy of approximations are applied to evaluate the EFG at the nuclei of an HCl molecule in several noncovalently bound clusters chosen to represent potential liquid or molecular crystal systems. A detailed assessment of such approximations is made for the Hartree-Fock treatment of electron-electron correlation (both in FDET and in the reference calculations for the whole cluster). The emerging choice of the optimal set of approximations is reconfirmed in calculations in which electron-electron calculations are treated at the MP2 level. Our optimized protocol produces average errors in the complexation-induced EFG shift on the order of 25% relative to conventional quantum mechanical calculations for the whole cluster. This protocol is shown to be numerically robust and leads to enormous computational savings compared to a complete quantum mechanical treatment of the embedded species and its environment. For a cluster comprising a Na+ cation and up to 24 water molecules, the computation time is reduced by a factor of 30,000 at the expense of introducing an error in the environment-induced EFG shift of 22%.

H3O+…Cl− ion pairs on the surface of concentrated hydrochloric acid: Reverse mass transfer of dissociated hydronium and chloride ions and the effect on separation at interface

The separation process in hydrochloric acid environments is determined by the interfacial chemistry of the acid. However, the surface species of concentrated acids are complex. The effect of dominant species on the surface of concentrated acids and their dissociation behavior on interfacial separation has been the focus of academic debate. The extraction and separation of two typical anions, PdCl42− and PtCl62−, with different hydration characters on the surface of concentrated hydrochloric acid were investigated by thin layer extraction (TLX). A new phenomenon was discovered that the effect of hydrochloric acid concentration, extractant concentration, organic film thickness, and shear flow rate on the extraction of easily hydrated PdCl42− anions is greater than that of hardly hydrated PtCl62−. However, during the conventional SX process, the phenomenon cannot be observed due to the continuous dispersion and aggregation of oil droplets. It found that HCl molecules only dissociate into solvated H3O+…Cl− ion pairs on the surface of concentrated hydrochloric acid, but not H3O+ and Cl− ions respectively. The concentration of dissociated H3O+ ions at the interface is lower than that in the bulk phase. The protonation of the A336 molecule promotes the migration of dissociated H3O+ ions in the bulk phase towards the interface. Because the PdCl42− anions are more likely to be hydrated than PtCl62− anions and combine with H3O+ ions, the orderly migration of H3O+ ions in the laminar boundary layer towards the interface drives the mass transfer of easily hydrated PdCl42− anions. The anion exchange between PdCl42− and Cl− ions associated with the A336 molecules results in a higher concentration of Cl− ions enriched at the interface than that in the bulk phase. The migration of easily hydrated Cl− ions towards the bulk phase would drag the water molecules around PtCl62− anions and therefore inhibit the mass transfer of PtCl62− anions. The orderly reverse migration of H3O+ and Cl− ions enhances the separation between easily hydrated PtCl62− and hardly hydrated PdCl42− anions. This study offers a new perspective on the dissociation of species on the surface of concentrated hydrochloric acid and its impact on separation processes.

Benchmarking noisy intermediate scale quantum error mitigation strategies for ground state preparation of the HCl molecule

Benchmarking noisy intermediate scale quantum error mitigation strategies for ground state preparation of the HCl molecule

Density functional theory study on the formation mechanism of CaClOH in municipal solid waste incineration fly ash.

Municipal solid waste incineration (MSWI) fly ash is defined as a kind of hazardous waste because of its high levels of multiple pollutants. The main component of MSWI fly ash is CaClOH, and the characteristics have not achieved consensus. And density functional theory (DFT) was used to calculate the formation process of CaClOH in this study, which mainly included HCl adsorption on CaO (0 0 1) surface and Ca(OH)2 (0 0 1) surface and the surface reaction process. The reaction mechanism was investigated. The results showed that the maximum adsorption energies of HCl on CaO and Ca(OH)2 surfaces reached - 195.17kJ/mol and - 83.48kJ/mol, respectively, representing strong chemisorption. The chemisorption process was shown as the adsorption of H atom on O site, and the adsorption capacity was reflected in the adsorption range of O site. The significant electron density overlap between O site and H atom meant that a new chemical bond formed, which made the adsorption structure stable. The adsorption energy of multi-HCl adsorption on the crystal surfaces was not proportional to the number of HCl molecule, indicating that the adsorption processes were influenced by each other. After surface reaction, the H-Cl bond was broken completely, and the structure of CaO and Ca(OH)2 changed to new structures. According to transition state (TS) search, the formation of CaClOH had a higher priority, easier than that of CaCl2, explaining the presence of CaClOH in fly ash. The study provides helpful information for the solidification treatment of fly ash.

Theoretical Study of Platinum Doped Anatase (101) Surface on Detecting Decomposition Production of Polyvinyl Chloride

The gas sensitivity of platinum doped TiO2 (101) to two kinds on polyvinyl chloride decomposition production, CO and HCl, were explored based on density functional theory. The binding energy, adsorption distance, charge transfer, and density of states distribution were simulated and discussed. The results suggest that the O oriented mode is probably the best mode for the CO gas molecules adsorption on the Pt-TiO2 and H oriented mode for the HCl adsorption system. HCl and CO molecules obtain electrons from Pt doped TiO2 surface. At room temperature, the recovery time of CO and HCl is 1.9743 × 10-10, 1.2094 × 10-10 respectively. HCl is easier to dissociate from Pt doped TiO2 surface with a little lower energy barrier compared to CO. This work provides theoretical adsorption information of Pt-TiO2 as gas sensor material for HCl and CO detection in the application of online condition monitoring and defect diagnosis in the power cables.

Mechanistic insight into acetylene hydrochlorination with Ru-ligands via dual activation promoted by metal-ligands cooperative catalysis

Ru-based catalysts have shown great potential for the environmentally friendly industrialization of acetylene hydrochlorination. However, the high cost and reduction of active sites in Ru catalysts have limited their practical applications. In this study, we propose a strategy to optimize the electronic structure of Ru single-atom catalysts by leveraging the strong coordination ability of ligands with the metal and apply this strategy to acetylene hydrochlorination. The experimental results verify that the performance of the catalyst increases with the increase of the ligand. Characterization results indicate that ligands not only optimize the electronic properties of Ru single atoms by forming a RuCl2-N structure, but also enhance the adsorption of reactants on the catalysts. DFT calculations reveal that the ligand-modified Ru species can efficiently adsorb and activate acetylene molecules, while the adjacent excessive ligand can adsorb and dissociate HCl molecules. This ultimately leads to an addition reaction between acetylene and HCl through a hydrogen overflow mechanism.

Energy spectrum and zero-temperature magnetic functions of a position-dependent mass system in a Pöschl-Teller-type potential constrained by a vector magnetic potential field

In this work, the position-dependent mass Schrödinger equation is solved with the Pöschl-Teller-like potential in the presence of magnetic and Aharonov–Bohm (AB) flux fields. The BenDaniel-Duke ambiguity parameter ordering is used to formulate the Hamiltonian operator for the system. An approximate analytical equation of the bound-state energy spectrum is obtained using the parametric Nikiforov-Uvarov solution technique along with a Pekeris-like approximation scheme. With the aid of the obtained equation for the energy levels, analytical formulas of magnetization and magnetic susceptibility at zero-temperature are derived and subsequently used to predict the physical properties of diatomic substances including the ground state H2, HCl, CO and LiH molecules. The expression for the bound-state-energy spectrum is used to generate numerical data for the molecules. The computed energy eigenvalues agree with the literature on diatomic molecules. The study revealed that in the absence of the external fields, the energy eigenvalues and magnetic susceptibility of the system are degenerate. However, with only a low intensity AB field, the degeneracy is completely eliminated from the energy states of the molecules.

HCl, DCl and TCl diatomic molecules in their ground state: predicting Born–Oppenheimer rovibrational spectra

The analytic Born–Oppenheimer (B-O) potential curve for the ground state of the molecule (H,D,T)Cl is constructed for the whole range of internuclear distances with an accuracy of 3–5 significant figures in comparison with the Rydberg–Klein–Rees-style potential curve derived from available experimental data on vibrational energies. With an accuracy of 3–4 significant figures, energy predictions are made for HCl (DCl, TCl) for the 836 (1625, 2366) B-O rovibrational bound states with maximal vibrational number and maximal angular momentum , including 24 (46, 63) weakly-bound states (close to the dissociation limit) with energies Hartree. The insufficiency of existing experimental data is indicated, and predictions for the bulk of the missing rovibrational states are made for all HCl, DCl, and TCl molecules.

DFT study of mercury adsorption on Al2O3 with presence of HCl

mercury emission control from flue gas is a crucial issue for environment protection. Alumina is an important alkali metal oxide for mercury adsorption in particulate, meanwhile is the potential adsorbent for mercury removal. The cognition on mercury heterogeneous reaction mechanism with alumina in presence of hydrogen chloride is inadequate. In this work, the DFT calculation was applied to detect mercury's chlorides adsorption on α-Al2O3 (001) surface, the Bader charge analysis was used to estimate electron transfer and the transition state theory was used to clarify reaction pathway and energy barrier, besides, the kinetic analysis based on Gibbs free energy was conducted to study the impact of temperature on chemical reaction. The results show that Hg can be captured by weak chemisorption on α-Al2O3 (001) surface with the adsorption energy of −56.37 kJ/mol, HgCl, HgCl2 are intensively bonded on surface with adsorption energies of −276.90 kJ/mol and −231.87 kJ/mol, the surface unsaturated Al and O atoms are the active sites. Charge transfer and PDOS analysis prove that the forming of covalent bonding is responsible for Hg species adsorption. Two possible reaction pathways of Hg oxidization to HgCl2 are discussed, in which a smaller energy barrier of 0.1 eV implies the dominant pathway 1 via Eley-Rideal mechanism: two adsorbed HCl molecules dissociate on surface and then react with one Hg atom. High temperature can promote the reaction rate constants of pathway 1 and 2, but is only favorable for reducing energy barrier of pathway 2.

DFT investigation of transition metal-doped graphene for the adsorption of HCl gas

Graphene-based toxic HCl gas sensors and adsorption materials are seldom reported. Utilizing density functional theory (DFT), the adsorption energy, charge density, and density of states, the sensitivity and recovery time of HCl gas adsorbed on graphene and six different transition metal-doped graphenes (TMDGs: TM = Ti, V, Cr, Mn, Fe, Co) were investigated. It indicates that TMDG has larger adsorption energy and chemical adsorption capacity than graphene. The Fe-doped graphene (FeDG) demonstrated better adsorption capacity and higher stability even at high temperature. The Mn- and Co-doped graphenes (MnDG & CoDG), exhibited magnetic changes after the adsorption of HCl molecules. Moreover, MnDG has both fast responsiveness and fast recovery time at a certain temperature. Thus, comparative speaking, among the six TMDGs, MnDG is the most suitable material for the detection of HCl gas, its magnetic property implied a novel application in HCl gas sensor.

Targeted Synthesis of an Highly Stable Aluminium Phosphonate Metal-Organic Framework Showing Reversible HCl Adsorption.

A concept for obtaining isoreticular compounds with tri- instead of tetravalent metal cations using highly acidic reaction conditions was developed and successfully applied in a high throughput study using N,N'-piperazinebis(methylenephosphonic acid) (H4PMP), that resulted in the discovery of a new porous aluminium phosphonate denoted CAU-60 ∙ 6 HCl. The high-throughput study was subsequently extended to other trivalent metal ions. Al-CAU-60 ∙ 6 HCl demonstrates reversible desorption of HCl (18.3 wt% loading) with three distinct compositions observed with zero, four or six HCl molecules per formula unit. Structural changes were followed in detail by powder X-ray diffraction, EDX analysis as well as IR spectroscopy. Rapid desorption of HCl in water within minutes and subsequent adsorption from the gas phase and from aqueous solution are shown. Furthermore, it is possible to adsorb HBr into the guest free Al-CAU-60 framework, demonstrating the high stability of this compound.

Targeted Synthesis of a Highly Stable Aluminium Phosphonate Metal–Organic Framework Showing Reversible HCl Adsorption

AbstractA concept for obtaining isoreticular compounds with tri‐ instead of tetravalent metal cations using highly acidic reaction conditions was developed and successfully applied in a high throughput study using N,N′‐piperazinebis(methylenephosphonic acid) (H4PMP), that resulted in the discovery of a new porous aluminium phosphonate denoted CAU‐60⋅6 HCl. The high‐throughput study was subsequently extended to other trivalent metal ions. Al‐CAU‐60⋅6 HCl demonstrates reversible desorption of HCl (18.3 wt % loading) with three distinct compositions observed with zero, four or six HCl molecules per formula unit. Structural changes were followed in detail by powder X‐ray diffraction, EDX analysis as well as IR spectroscopy. Rapid desorption of HCl in water within minutes and subsequent adsorption from the gas phase and from aqueous solution are shown. Furthermore, it is possible to adsorb HBr into the guest free Al‐CAU‐60 framework, demonstrating the high stability of this compound.